Increasing Stability of Meso /Micro Milling Cutting by means of Ultrasonic Vibration Assisted Machining Paolo Parenti*, Chaneel I. Park**, Simon S. Park**, Massimiliano Annoni* *Dept. of Mechanical Engineering, Politecnico di Milano **Dept. of Mechanical and Manufacturing Engineering, University of Calgary Corresponding Authors: VMPT 2014 Prof. Simon Park [email protected] http://www.ucalgary.ca/medal/ Tel: 403 220 6959 Prof. Massimiliano Annoni [email protected] http://www.mecc.polimi.it/ Tel: (+39) 02 2399 8536 Micro Engineering Dynamics Automation Lab (MEDAL) Milling Process instability (Regenerative Chatter ) • Poor Surface finish • Reduced Productivity • Excessive Tool Wear • Tool Breakage Receptance Coupling (RC) Ultrasonic Vibration Assisted Machining • Chip Removal (cutting kinematics and cutting action) • Cutting force reduction (friction) • Machinable Materials (hard/brittle) • Burr formation • Toll Wear (including thermal and chemical) Experimental Setup Kern CNC machining center Spindle: 60000 / 150,000 rpm Resolution 0.1 μm Positioning tolerance ±1.0 μm Controller Heidenhain End mill 2 Flutes Diameter=500μm Edge radius≈2μm Helix=30° / Clearance=10° Young’s Module≈690Gpa Dynamic Charachterization Single Cristal Piezo Cylinder RF Amplifier Signal Generator Process Improvement • Cutting Coefficients reduction (rake angle) • Tool dynamic modification (clamping) • Increased Process damping Effects on Cutting Stability R. Rahnama et al. / JMPT 209 (2009) 5766–5776 M.Goletti (2009) Single-Axis Vibration at Ultra-High Frequency (100KHz-3MHz) 1st tool mode • Reduction of cutting forces are measured through dynamometer during stable cutting EMA FEM 3-Axial Vibration at 20KHz Setup # 2 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0 5 10 15 20 25 30 35 40 45 50 55 60 [s] Force X [N] Monitoring signals (chatter detection) • Acoustic Emission • Accelerometers • Forces (up to 5KHz) Piezo - Electric Actuators Lobes Diagram Calculation and Verification tool tool WP WP • Stability Lobes diagram is verified with and without application of UVAM technique Cutting tests GOALS: • To verify experimentally the force reduction by applying UVAM in different directions with very high vibration frequency • To investigate the increased cutting stability with respect to the regenerative chatter phenomenon • Chatter detection is based on AE sensor/ Accelerometer • Effects of high assisting frequency (>100KHz) are investigated and compared with lower frequency (20KHz) • Process cutting modelling through Mechanistic and FEM approach are foreseen • Industrial exploitability of the solution is also addressed to avoid